1. Field of the Invention
The present invention relates to a cube puzzle, and more particularly to a combined structure of an educational five-by-five cube puzzle having smooth rotation without unrotatable layers of blocks due to slightly skew block alignment.
2. Description of the Related Art
Conventional cube puzzles have different choices of cube sizes, such as 2×2×2, 3×3×3, 4×4×4 and larger cube sizes. As the cube sizes increase, the cube puzzles become more and more complicated in terms of the individual parts and the entire structure. Basically, each conventional cube puzzle has a central shaft and multiple blocks mounted on the central shaft and being pivotally rotatable with respect to the central shaft so as to generate diversified cube puzzles. Different colors and patterns are formed on the sides of each block. To solve a cube puzzle, users must keep rotating the blocks of the cube puzzle until each side of the cube puzzle shows a same color.
The cube puzzles have been widespread and popular since the first appearance, and the combined structure thereof has been also developed for over three decades. However, as far as the 5×5×5 cube puzzles are concerned, although each layer of the cube puzzles is normally rotatable, the blocks of each layer of the cube puzzles to be rotated may be locked and unrotatable when the layer of blocks slightly deviates from their supposed position. Such phenomenon arises from excessive friction among the blocks and low manufacturing tolerances of the gaps between the blocks, and thus results in an awkward operation and unsmooth moves of the cube puzzles when the user attempts to solve the cube puzzles.